Production of composite structures

ABSTRACT

AN IMPROVED DEVICE FOR HELICLLY AND SPIRALLY WINDING A FLEXIBLE RIBBON ABOUT A TUBULAR WORKPIECE. MEANS ARE PROVIDED FOR MOVING THE WORKPIECE ABOUT ITS LONGITUDINAL AXIS WHILE ROTATING ABOUT THE HORIZONTAL AXIS SIMULTANEOUSLY. A FOAM LIKE FILLER MATERIAL IS PROVIDED BETWEEN THE WORKPIECE AND THE SPIRALLY WOUND RIBBON FORMING A SHEATH. THE FOAM LIKE MATERIAL IS INTRODUCED ONTO THE SPIRAL RIBON BY WAY OF NOZZLES. VACUUM MEANS ARE PROVIDED ON THE UNDERNEATH SIDE OF ENDLESS BELT CONVEYING THE RIBBON TO BE COATED WITH FOAM. THE RIBBON WITH FOAM IS TANGENTIALLY FED ONTO THE WORKPIECE. A SECOND DRIVE ASSEMBLY IS PROVIDED AFTER THE RIBBON APPLYING STATION TO PROPEL THE THUS COMPOSITE PRODUCT.

June 1974 o. G. KEITH ETAL 3,817,813

PRODUCTION or courosns s'rRUc'ruREs Original Filed Feb. 22. 1971 9Sheets-Sheet 1 FIG. 1

'ITD

June '18, 1914 rrH ETAL 3,817,813

PRODUCTION OF COMPOSITE STRUCTURES Original Filed Feb. 22. 1971 9Sheets-Sheet 2 FIG. 2

June 18, 1974 Original Filed Feb. 22. 1971 D. s. KrrH ETAL PRODUCTION OFCOMPOSITE STRUCTURES F IG 3 fai 9 Sheets-Sheet I June 18, 1914 1 n' ETAL3.817.813

PRODUCTION OF COMPOSITE STRUCTURES Original Filed Feb. 22. 1971 9Sheets-Sheet 5 DRIVE SHAFT (1) DRIVE SHAFT 2) I CLUTCH DRIVE TO RIBBONFEED DEVICE June 18, 1974 n'H ErAL 3,817,813

PRODUCTION OF COHPOSITE STRUCTURES Original Filed Feb. 22. 1971 9Sheets-Sheet 6 u June 18, 1974 n- ETAL PRODUCTION OF courosnss'rauc'runms 9 Sheets-Sheet '7 Original Filed Feb 22. 1971 June 18, 1974D. G. KEITH ETA!- 3.317.313

PRODUCTION OF COMPOSITE STRUCTURES Original Filed Feb. 22. 1971 9Sheets-Sheet 8 June 18, 1974 D. G. KEITH ETAL 3,817,813

menus-non OF COHPOSITE s-rnucrunas Original Filed Feb. 22. 1971 9Sheets-Sheet 9 FIG. 9

United States Patent rm. oi. B31c 3/00 US. Cl. 156-429 12 ClaimsABSTRACT OF THE DISCLOSURE An improved device for helically and spirallywinding a flexible ribbon about a tubular workpiece. Means are providedfor moving the workpiece about its longitudinal axis while rotatingabout the horizontal axis simultaneously. A foam like filler material isprovided between the workpiece and the spirally wound ribbon forming asheath. The foam like material is introduced onto the spiral ribbon byway of nozzles. Vacuum means are provided on the underneath side ofendless belt conveying the ribbon to be coated with foam. The ribbonwith foam is tangentially fed onto the workpiece. A second driveassembly is provided after the ribbon applying station to propel thethus composite product.

This is a division, of application Ser. No. 117,457, filed Feb. 22,1971, now US. Pat. No. 3,778,322.

This invention relates to a process and machinery for the production ofcomposite structures, and in particular composite rods or tubes, byhelical (or spiral) winding.

In British patent specification 1,151,884, there is described a processfor the production of composite tubes which comprises rotating a tubearound its longitudinal axis and moving it along said axis, supplying aribbon coated with a foamable composition tangentially to the rotatingtube and at an angle of less than 90 to the longitudinal axis of thetube so that the coated ribbon forms a spirally wound envelope or sheatharound the tube with the foamable composition in the annulus, andallowing the foam to expand and cure. In accordance with the processdescribed, the ribbon is drawn on to the tube by rotational andlongitudinal forward movement of the tube and the size of the ultimatefoam layer (and hence the overall diameter of the composite tube soproduced) is controlled more or less by the amount of foamablecomposition deposited on the ribbon, the conditions of foaming, and theback tension, if any, exerted on the ribbon. The uniformity of theproduct, therefore, is dependent upon the maintenance of a steady rateof deposition of the foam forming composition and of unchangingcondition e.g. of humidity or temperature, during the foam rise.

According to the present invention, we provide a process for theproduction of spirally wound products which comprises advancing atubular or rod-like workpiece along its longitudinal axis while rotatingit about said axis, by positive drive feeding a flexible ribbon ashereinafter defined tengentially to the rotating advancing workpiece ata preselected rate and preselected angle of less than 90- to thelongitudinal axis thereof such that the resultant spiral ribbon windingsform a sheath enveloping a greater crosssectional area than that of theworkpiece, providing a filling material in the space between theworkpiece and the spiral ribbon windings and bonding the spiral ribbonwindings together or to the workpiece or both. The process isparticularly suitable for continuous operation.

3,8 l 7,8 13 Patented June 1 8, 1 974 While the process is particularlyapplicable to the use of foamable synthetic resin as the fillingmaterial, which composition is allowed to expand and set to provide thecomposite end product, other filling materials may also be used, e.g.mineral flocks and fibres. Viscous or liquid filling materials may beused if the process is adapted so that the workpiece is fed verticallyor substantially so.

THE WO RKPIECE The workpiece may be solid, e.g. as in a rod, or hollowas in a pipe or tube, and is preferably but not necessarily circular orsubstantially circular or at least symmetrical in cross-section. Theworkpiece may form an integral part of the composite product or may bewithdrawn from the composite product on completion of the process toleave a tube in which case it may be desirable to pre-coat the workpiecewith a release agent to prevent adhesion of the filler, e.g. foam, tothe workpiece. Hollow workpieces may be self-supporting or not and inthe latter case they may be supported during the process e.g. by theprovision of suitable cores or, for example, by internal fluid pressure.The cores may be withdrawn from the finished product and may be of thecollapsible type to aid Withdrawal.

The workpiece is preferably supplied continuously, for example byjoining lengths together end-to-end as they are fed to the ribbonwinding station. The joining may be of a permanent nature, e.g. bywelding, or it may be temporary, e.g. by use of temporary couplings. Inthe latter case, the composite product of the process may be dividedinto lengths, e.g. by sawing through the outer spirally wound cover andthe filling material at the points of temporary coupling and thenuncoupling the workpieces.

In an alternative process, the workpiece may be formed continuously andin situ, e.g. by extrusion using a rotating extruder or by spirallywinding one or more plies, if necessary on to a hollow or solidsupporting core.

The workpiece may be of any suitable material, e.g. metal, wood, paper,earthenware, ceramic, concrete, cardboard, rubber, glass, textile,plastic, reinforced plastic and resin impregnated fibre; the plastic maybe either natural or synthetic and either thermoplastic or curable, andmay be foamed, if desired.

The workpiece may itself be of composite, e.g. laminated, construction,particularly in the case where it is formed from a number of plywindings. It may also, for example, comprise an end-to-end series oftins, cans or other containers carrying a variety of fillings, e.g. foodor other perishable or fragile goods requiring insulation or protection.

The workpiece may be of any desired diameter, e.g. from one inch or evenless to several feet.

THE FLEXIBLE RIBBON The term flexible," as used herein with reference tothe ribbon, means only that the ribbon is spfficiently flexible to becoiled into a sheath of the desired diameter. Thus, for example, stiffribbons that may be unsuited to coiling into small diameters inaccordance with our process may be quite suitable and even desirable forcoiling into larger diameters.

The width of the ribbon is not critical but for convenience and ease ofoperation it is preferred to be such that the angle at which the ribbonis fed to the workpiece is not more than about -80 and not less thanabout 55 to the longitudinal axis thereof. However, foam control, theachievement of an economical rate of production and other factors mayrequire one to operate outside this preferred range of angles.

The ribbon may be formed of any suitable material, e.g. paper,cardboard, woven and unwoven textile, glass fibre, metal, rubber,plastic, reinforced plastic and resin-im' pregnated fibre. The plasticmay be natural or synthetic, and either thermoplastic or curable. Ifdesired, the ribbon may be of composite, e.g. laminated construction,for example as in plastic-coated paper or plastic-coated metal foil.

FOAM-COMPOSITION While as stated hereinbefore many different materialsmay be used as the tiller, the preferred material is a synthetic resinfoam e.g. as based on a foamed or foamable composition.

The foamed or foamable composition may be based on a polymeric materialand while the use of thermoplastic polymers such as polyamides,polyesters, polyacetals, polycarbonates, polysulphones and polymers andcopolymers of ethylenically unsaturated monomers, e.g. ethylene,propylene, 4-methylpentene-l, styrene, vinyl chloride, acrylonitrile,butadiene and acrylic esters, is not excluded, it is generally preferredto use foamable compositions based on curable polymer systems, e.g.curable polyurethanes, phenol/formaldehyde resins, amine/formaldehyderesins, epoxy resins and compositions of the kind comprising at leastone polymerisable vinyl ether containing at least two vinyl groups permolecule as described in British patent specification No. 991,970. Theprocess is particularly suitable for use with polyisocyanurates, e.g. ofthe kind described and claimed in British patent application Nos.18,116/65, 17,730/66, 13,250/67 and 7,772/68, whose sensitivity tends torender them diflicult to use with, for example, the process of Britishpatent specification 1,151,884.

The composition may be formulated to give rigid or flexible foams, asdesired, but rigid foams are generally preferred because of theirphysical properties such as crush resistance, etc. The foams may also bepredominantly open-celled or closed-celled, as desired, it beingunderstood that in general the thermal insulation characteristics areimproved with increase in closed-cell content.

The foamable or foamed compositions based on thermoplasts will generallybe applied hot, at a temperature above the softening point of thethermoplast, and may be hardened or solidified when the desired extentof foaming has been achieved by allowing them to cool. Foamablecompositions based on curable systems, on the other hand, may be appliedhot or cold and further heating or cooling may be applied as desired toeffect or control cure. Examples of such compositions are those based onpolyurethane and polyisocyanurate-foaming mixtures.

THE PROCESS In accordance with the process of the invention, by positivedrive the flexible ribbon is fed tangentially to the rotating advancingworkpiece at a rate and angle to the longitudinal axis such that theresultant spiral ribbon windings define a sheath enveloping across-sectional area greater than that of the workpiece thus defining aspace between the external surface of the workpiece and the internalsurface of the sheath in which a filler, e.g. foamable composition, maybe placed. In other words, by positively driving the ribbon forward at aspecified angle and rate, the geometry of the helically produced sheathis fixed and a space is defined between the sheath and the workpiecewhich the foamable composition may expand within to fill. This is inclear contradistinction to the process described in the aforementionedBritish patent specification No. 1,151,884 where the ribbon is drawn onto the workpiece by the rotation thereof and the size of the gap filledby the foam is determined essentially by the extent to which thefoamable composition expands. Thus, in the process described in theaforementioned patent specification the foamable composition expandsfreely and the ribbon adapts itself to sheath it, while in the processof the present invention, the space is defined and the foamablecomposition expands to fill it. It will therefore be recognised that theprocess of our invention is more readily adaptable to the continuousproduction within required limits of tolerance of composite products ofa specified and substantially uniform outside diameter irrespective ofminor irregularities in the cross-section of the workpiece, the natureor rate of delivery of the foam composition, the conditions extantduring the expansion and/or setting of the foamable composition, and anysmall changes in the back tension of the ribbon, e.g. of the kind thatwould occur through blocking or sticking on the reel. It is also morereadily adaptable to the use of foamable compositions of highsensitivity such as those based on polyisocyanurates.

The spiral ribbon windings may be bonded together and/ or to theworkpiece by means of the filling material where its nature allows.Thus, in the case of many foamable compositions which are based onpolymeric materials and pass through a tacky phase during theirexpansion and/or hardening, it may be possible to effect a bond alongthe helical joint line between the axially adjacent spiral windings andto bond these to the workpiece by means of the foam. Alternatively oradditionally, the bonding of the ribbon windings to each other may beachieved by other means, e.g. by the use of adhesive tapes, by welding,by glueing or by so shaping the edges of the ribbon that they interlock.Equally, the spiral windings may be bonded to the workpiece by bondingthe filling material to the workpiece, e.g. by means of an adhesive, andbonding the spiral windings to the filling material in like manner.

The foam may be provided in the space in any suitable manner but a verymuch preferred method is to deposit a foamable composition on to thesurface of the flexible ribbon at a point before the ribbon is fed on tothe workpiece, and to feed the ribbon to the workpiece with the foamablecomposition between the ribbon and the workpiece. By suitably adjustingthe conditions of operating this method, it can be arranged for thefoamable composition to lie on a substantially horizontal surface duringthe critical initial period of rise, thereby ensuring optimum conditionsfor the production of columnar cells perpendicular to the surface of theribbon which are a prerequisite for the formation of good quality foam.Most preferably, the surface of the ribbon is maintained substantiallyhorizontal in its travel from the point at which the foamablecomposition is deposited on it to the point at which it is fed on theworkpiece.

Other methods of providing the foam in the product include, for example,depositing the foamable composition on the outside of the workpieceprior to winding on the ribbon or feeding the composition into the spacebetween the sheath and the workpiece as the former is being formed. Inboth these methods, however, the rotary motion of the workpiece maycreate difiiculties in obtaining an even deposit because of flow of thecomposition under the influence of gravity.

Irrespective of the manner in which the foamable composition is providedto form the foam in the space, it is preferred that it is in contactwith the surfaces of both the workpiece and the sheath before it isfully set (e.g. cooled or cured as the case may be) in cases whereadhesion to both surfaces is desired so that the foam bonds adjacentribbon windings to each other and to the workpiece. Alternatively,adhesion may be aided or effected by application of a suitable adhesiveto one or each surface before it comes into contact with the foamablecomposition.

In the very much preferred case where the foamable composition isdeposited on the ribbon, it is preferred that at least some but not allof the expansion of the foam is completed before the ribbon is fed on tothe workpiece so as to reduce or avoid slip between adjacent helices ofthe ribbon due to excessive further expansion of the foam in the spacebetween the helically wound sheath and the workpiece.

Where it is desired for the axially adjacent ribbon windings to overlap,it is further preferred that the surface of that portion of the width ofthe ribbon that is involved in the overlap (hereinafter referred to forconvenience as the lap Width) is free of foamable composition, orsubstantially so, since otherwise, the composition will be squeezed outof the overlap as the helices are formed and at the least will form anunsightly mark or smear on the outside surface of the composite product.At worst, it may deposit itself on the machinery or even jam it. Inorder to avoid this, it can be arranged for the composition to bedeposited on only part of the width of the ribbon, leaving the lap widthuncoated, or alternatively the lap width may be protected duringfoaming, e.g. by application of a masking tape which may then be removedbefore winding. On the other hand, it may be desirable to provide a verythin coating on the lap width to act as an adhesive, e.g. by overspray.

It is further preferred where overlapping is desired that the lap widthis stretched or expanded to accommodate the overlap so as to avoidcrinkling. This may be effected, for example, by creating a thermaldifferential across the width of the ribbon so that the lap widthexpands longitudinally with respect to the remaining width and/or isrendered more easily stretchable. Alternatively or additionally, the lapwidth may be stretched mechanically with respect to the remaining width.

In order to provide an even and uniform deposit of foamable compositionon the ribbon, it has been found preferable to deliver it from a nozzleor series of nozzles which reciprocate across the Width of the ribbon.By provision of means for adjusting the throw of the reciprocatingmember, a single delivery device may be used for ribbons of any widthand for any desired overlap.

It is, of course, highly desirable to provide suflicient foamablecomposition to fill the space between the workpiece and the sheath withfoam at the desired density. It is very much preferred that the foamablecomposition is provided in an amount which gives slightly in excess ofthe desired amount. The use of a substantial excess, however, may resultin a foam of substantially reduced physical properties, especiallycompressive strength and bond strength. In accordance with a furtherpreferment, therefore, the pressure exerted by the foam in the nipbetween the ribbon and the workpiece is continuously measured and theamount of foamable composition that is deposited per unit area of theribbon is adjusted to maintain the pressure between predeterminedlimits.

The means for feeding the ribbon forward at the desired rate ispreferably situated at a point as near as possible to the longitudinalaxis of the workpiece so as to obtain the maximum control. Where theribbon is coated with fomable composition, the driving force can withcase only be applied to the under-surface of the ribbon if damage to thefoam and/or clogging of the machinery is to be avoided. This may beachieved, for example, by use of a feed device co-operating with theunder-surface of the ribbon by application of vacuum, as described morefully hereinafter.

The driving force or forces for applying the combination of forward androtary motion to the workpiece and to the composite product may beapplied either to the workpiece at a point before the ribbon is fed onto it, or to the product, or both, as convenient. There are inherentproblems, associated with the state of the foam layer in the product,which create difficulties in applying a driving force to the productwithout damaging the foam, and while we have devised machinery which iscapable of driving the product without causing this damage is may oftenbe preferred to apply the drive only to the workpiece before the foam isapplied. However, where the workpiece is being formed in situ, e.g. byspirally winding one or more plies or by use of a rotary extruder, itmay be impossible or inconvenient to drive the workpiece, and the drivemay then have to be applied to the composite product. Where possible, itis much preferred to drive both the workpiece and the composite productsynchronously so that there is substantially no torque on theworkpiece/composite product at the point where the ribbon is fed on toit (the winding station), thereby reducing any torsional stress on thefoam at this point.

Heating the foamable composition and/or heating or cooling the compositeproduct may be found desirable in order to accelerate and/or provide afurther degree of control of the rise and setting of the foam.

The composite product is preferably sawn up into lengths when the foamis in a sufficiently stable state to be handled and the lengths may alsobe sawn lengthwise, if desired, e.g. to provide arcurate laggingsections for pipes.

THE MACHINERY In accordance with a further embodiment of the invention,machinery is provided for the production of composite products by themethod hereinbefore defined comprising in combination (i) support meansfor the machine components, (ii) means for supporting a rod like ortubular workpiece, (iii) means for continuously moving said workpiecealong its longitudinal axis past a ribbon winding station, (iv) meansfor simultaneously rotating said workpiece about its longitudial axis,(v) continuous supply means for a flexible ribbon, (vi) drive means forfeeding the ribbon forward to the rotating advancing workpiece at theribbon winding station at a preselected rate, (vii) means for guidingthe ribbon tangentially on to the workpiece at a preselected angle ofless than to the longitudinal axis thereof at the ribbon windingstation, (viii) means for providing a filler material, especially foam,in the space between the workpiece and the sheath formed therearound bythe spirally wound ribbon, and (ix) guide and support means for thecomposite product so formed.

In a much preferred embodiment where the filler material is foam, themeans for providing foam in the space between the workpiece and thesheath formed from the ribbon comprises means, situated on the path ofthe ribbon between its point of supply and the Winding station, fordepositing a controlled quantity of a foamable composition on theribbon. In this embodiment may also be provided (a) means forcontrolling the width of the deposit on the ribbon so as to leaveuncoated part of the width adjacent one edge (hereafter referred to asthe lap width) for overlap if desired; (b) means for extending the lapwidth longitudinally with respect to the remaining width, e.g. bythermal expansion and/or by mechanical means so as to accommodate theoverlap, and/or means for rendering the lap width relatively more easilystretchable than the remaining width, e.g., by thermal treatment; and/or(0) means for controlling the temperature of the foamable compositiondeposited on the ribbon and possibly also for thermally treating theribbon before the foamable composition is deposited on to it.

Where the ribbon is of a material having an adequate thermal coefficientof expansion, the means for extending the lap width with respect to theremaining width of the ribbon may comprise means for causing a suitabletemperature differential across the width of the ribbon. The desireddifferential can readily be calculated from knowledge of the intendeddiameter of the sheath and the thickness and coefficient of thermalexpansion of the ribbon.

Alternatively or additionally, mechanical means for differentiallyextending the ribbon across its width may be provided. For example, theribbon may be passed under tension through a bank of e.g. frustoconicalrollers arranged to stretch the lap Width of the ribbon with respect tothe remaining width. If desired the lap width may be thermally treatedto render it more easily stretchable before it is subjected to themechanical treatment.

Preferably, the means for depositing the foamable composition comprisesat least one foam composition delivery nozzle adapted to reciprocateacross the width of the ribbon, and means for reciprocating it. Theposition of nozzle may also be adjustable in the direction of travel ofthe ribbon.

Any suitable means may be provided for controlling the temperature ofthe foamable composition on the ribbon. For example, heaters or coolingmeans may be provided above and/or below the ribbon and may be arrangedto provide a temperature gradient along, across and/ or through thedepth of the foamable composition. The ribbon may also be preheatedbefore it receives the foamable composition. If desired, the ribbon maybe passed through a temperature controlled enclosure before and/or afterthe foamable composition has been deposited on it.

The ribbon may also be supported during the deposition of the foamcomposition and/or subsequently up to or near the point at which it isfed to the workpiece. Conveniently it is supported and located laterallyon a table which is pivotable in a horizontal plane about the workpiecewhere the ribbon is fed to the workpiece. Most suitably, it is pivotableabout a vertical axis which passes through the longitudinal axis of theworkpiece and the centre line of the ribbon where it is fed on to theworkpiece, thereby providing a means of controlling the angle at whichthe ribbon is fed to the workpiece. Preferably, the table is slightlyconvexly curved along its length thereby aiding maintenance ofcontinuous contact between the ribbon and the table and the avoidance ofair pockets, and also reducing the danger of the edges of the ribboncurling up.

The means for feeding the ribbon to the workpiece is preferably sited asnear as possible to the point at which the ribbon is guided on to theworkpiece. Profitably, the feed means may be piwoted in a horizontalplane about the workpiece where the ribbon is fed to the workpiece.Ideally, it is pivotable about a vertical axis which passes through thelongitudinal axis of the workpiece and the centre line of the ribbonwhere it is fed on to the workpiece, thereby providing further andpotentially more positive control of the angle at which the ribbon isfed to the workpiece. To this end, the feed means may be located on thetable. Means may also be provided responsive to incoming informationconsisting of the desired outside diameter (D) of the composite productand the effective width (w.) of the ribbon (that is the width of theribbon less that used for overlap, if any, to automatically set the 9 atwhich the ribbon is fed to the workpiece in accordance with therelationship Cos 9=w.(1rD)- Where the ribbon carries a coating offoamable composition, the feed means is preferably a vacuum haul offdevice, for example an impeller, e.g. an endless belt, to which theunder-surface of the ribbon is applied by vacuum suction, thus avoidingcontact with the coated surface of the ribbon and possible damage to thefoam or clogging of the machinery.

In accordance with a preferred embodiment, the feed means comprises aframe carrying (i) a vacuum box open at the top, (ii) beyond oppositeends of the box parallel rollers for supporting an endless belt, (iii)means for driving at least one of the rollers, (iv) an endless belt ofporous or perforated material adapted to travel across the open top ofthe vacuum box, (v) preferably a vacuum seal between the top edges ofthe box and the belt, and (vi) means for connecting the interior of thebox to a vacuum pump. Preferably, the top of the box may be closed by aperforated or slotted sheet or else the box is provided withlongitudinal ribs, in order to provide additional support for the beltduring its travel across the box.

Any suitable drive means may be used for moving the workpiece past theribbon winding station and for rotating it, and the drive may be appliedto the work piece at a point prior to the ribbon winding station and/orto the composite product at a point beyond the ribbon winding station.The drives may comprise, for example, lapped belts or skew rollers butin a much preferred embodiment, the rotary and linear motions areapplied to the workpiece and/or the product by independent andseparately isolatable means.

In accordance with this preferment, the drive assembly for the workpieceor product comprises (a) a base having mounted thereon,

(b) a first unit and a second unit through each of which the workpieceor product may move along its longitudinal axis, each of said unitsbeing separately rotatable about said axis, and

(c) means for rotating each of said units around said axis, and whereinthe first unit has mounted thereon means for propelling the workpiece orproduct along its longitudinal axis, and the second unit isco-operatively engaged to the propelling means whereby in operation thepropelling means is set in motion by causing relative rotary motionbetween the first unit and the second unit and the speed of thepropelling means is proportional to the difference in the rotationalspeeds of the first and second units.

Preferably the units of the drive assembly are capable of beingsynchronously coupled whereby at any linear throughput velocity orrotational speed the pitch of the helical path along which the surfaceof the workpiece or product is moved remains constant. For example, thedrive to each of the two units may be taken from a common drive shaft,there being a variable speed unit, e.g. a Kopp variator, between one ofthe unit drives and said drive shaft or between the unit drives wherebythe setting of the variable speed unit determines the pitch of thehelix. While said units preferably have this capability of synchronousoperation, it will readily be appreciated that rapid synchronous changesof pitch may also be achieved thereby allowing for fine pitch controlwhile running.

In a preferred embodiment of the drive assembly, the means forpropelling the workpiece or product along its longitudinal axis comprisea plurality of impellers radially disposed relative to the axis ofrotation of the first unit. Preferably there are at least three suchimpellers, e.g. disposed at to each other. Each impeller may comprise,for example, one or more rollers or, more preferably, endless belts,thereby allowing the pressure necessary for gripping the device to bedistributed over a large surface area thus reducing the danger of localoverloading and aiding the handling of delicate and fragile workpieces,e.g. thin walled tubes and composite products containing a foam fillingin the walls.

In yet a further preference, means are provided for adjusting thedistance of each impeller from the rotational axis of the first unitwhereby workpieces and products of non-circular, polygonal, or evenasymmetric cross-sectional sizes and shapes may be accommodated. Inanother preferred embodiment means are provided for adjusting thedistance of each radially disposed impeller from the rotational axis ofthe first unit simultaneously with the distance of each other impellertherefrom, thereby providing an automatic centering facility which isespecially desirable in many applications.

In accordance with a still further preferment, the driving surfaces ofthe means for propelling the workpiece, e.g. the radially disposedimpellers, are resilient, thereby tolerating some girth variation in theworkpiece. For example, the impellers may comprise endless belts with aresilient, e.g. foam rubber, driving layer or a plurality of resilientdriving pads. Given sufficient resilience, even flanged tubes may betreated using our machine. Thus, in accordance with the preferredembodiment, a rotary drive assembly is provided which may driveinvariantly on a helical path whose diameter is larger than the greatestcross-section of the workpiece or product to be driven and couples tothe said workpiece or product by resilient or compliant facings whichwill tolerate a range of girth variation in the workpiece or product.

In a convenient embodiment, the second unit of the drive assemblycomprises an annular wheel (that is, a

ring gear with the teeth facing inwards) which is cooperatively engagedto one or more, and preferably all, of the radially disposed impellers(or groups of impellers) by means of associated epicyclically disposedpinions which are drivably coupled to the impellers, or groups ofimpellers, e.g. by bevel gears.

Two such drive assemblies may be used, one sited before the ribbonwinding station and adapted to drive the workpiece and one sited beyondthe ribbon driving station and adapted to drive the composite product.By this means, the potentially disruptive influences of, for example,coupling up workpieces for feeding to the winding station or sawing upthe product, may be isolated from the ribbon winding station thusimproving the uniformity of the product. To minimise torque effects, thetwo drive assemblies are preferably coupled so that the means foradvancing the workpiece to the ribbon winding station and the means forwithdrawing the composite product from the ribbon winding stationoperate at the same linear velocity, and the means for rotating theworkpiece and composite product operate at the same rotational speed. Itmay also be desirable to couple the linear drive means synchronouslywith the rotational drive means thereby ensuring the maintenance ofconstant pitch during any change of linear throughout or rotationalspeed.

It will be recognized that the drive assemblies described above areparticularly well adapted to be coupled together since unlike skewdrives or lapped belts their operation is not upset by any change indiameter of the workpiece or composite product.

To provide additional control of the process, preferably means are alsoprovided for coupling the means for rotating the workpiece and/orcomposite product in the appropriate drive assembly with the means forfeeding the flexible ribbon to the workpiece whereby for any givenoutside diameter for the product and any given width of the ribbon, theflexible ribbon is supplied at the correct rate for any speed ofrotation of the workpiece or product. The association between theseparameters may be derived by reference to FIG. 1 of the drawingsaccompanying the provisional specification and is to the effect that therate at which the ribbon is to be supplied is determined by therelationship where v is the length of ribbon required per revolution, Dis the desired outside diameter of the composite product and 6 is theangle at which the ribbon is fed to the workpiece (ie the included anglebetween the long axis of the ribbon and the longitudinal axis of theworkpiece), and

where w is the effective width of the ribbon (i.e. width of ribbon lesswidth of overlap, if any).

Further control may be obtained by providing means for sensing thepressure of the foam in the nip between the ribbon and the workpiece andmeans for controlling the amount of foamable composition deposited perunit area of ribbon to maintain said pressure within predeterminedlimits. In accordanoe with one method of achieving this, resilientlymounted means are provided for displacing the ribbon from its naturalstraight line path between the ribbon drive means and the point wherethe coating of foam on the ribbon first comes into contact with theworkpiece, said means being movable to increase or decrease thedisplacement of the ribbon from said straight line path, and theposition of said means being adjusted such that at a given positivedisplacement, the displacing force exerted by said means is just equalto the counter force exerted by the desired foam pressure (or thickness)at the nip so that any increase or decrease in the foam pressure (orthickness) at the nip is reflected by a change in the position of saiddisplacing means. Conveniently the displacing means may be a roller,plate or bar mounted transverse the ribbon and in contact with theundersurface thereof and may be spring loaded or operatively connectedto a load cell. The position of said displacing means may be indicatedvisually by a pointer on a dial and/or any change in position of saidmeans beyond predetermined limits may be indicated visually or audibly,e.g. by lights or bells. Preferably, however, the system is selfadjusting by providing means responsive to any change in position ofsaid displacing means from its median position for adjusting the rate ofdeposition of foam composition per unit area of ribbon to restore saiddisplacing means to its medium position.

For use in the process of our invention wherein the workpiece iscontinuously formed in situ by extrusion, the machinery of the inventionadditionally comprises anterior to the ribbon winding station a rotaryextruder.

For use in the process of our invention wherein the workpiece iscontinuously formed in situ by spiral winding of one or more plies, themachinery of the invention additionally comprises anterior to the ribbonwinding station means for continuously supplying one or more plies offlexible material and means for forming said ply or plies into aspirally wound tube.

A mandrel may be provided for supporting a hollow workpiece up to and/orat or beyond the ribbon winding station. In order to aid the continuouswithdrawal of the workpiece from the mandrel, the latter may be tapered.Alternatively, it may be porous for at least part of its length and beconnected to pressurised fluid supply means to provide a fluidlubricating layer between the outer surface of the mandrel and the innersurface of the hollow workpiece. Suitably, the mandrel has a non-poroushead and porous tail and the tail is of slightly smaller crosssectionthan the head. The mandrel is particularly useful in the treatment ofnon-self-supporting tubular workpieces such as tubes spirally andcontinuously wound from paper ply immediately prior to the treatmentstation. It may be rotatable, if desired, and may rotate freely or bedriven at a rotational speed at least equal to that of the workpiece itsupports. A suitable mandrel is described in our copending applicationNo. 9,956/69.

The invention is now illustrated with reference to preferred embodimentsthereof and with the aid of FIGS. 2 to 9 of the drawings accompanyingthe provisional specification in which FIG. 2 is an isometric sketch ofone form of machine suitable for use in the process of the inventionwith parts of some components cut away to expose their internalconstruction,

FIG. 3 is a cross-section through the machinery along the line AA ofFIG. 2,

FIG. 4 provides a detailed cross-sectional side elevation of the driveassembly identified generally by reference numeral 14 in FIG. 2,

FIG. 5 shows one method of coupling the drive assembly for the workpiecewith the drive assembly for the composite product and of coupling one ofthe drive assemblies with the ribbon feed means.

FIG. 6 is an enlarged perspective view, part cut-away, of one form offeed means for the flexible ribbon, identified generally by referencenumeral 11 in FIGS. 2 and 3.

FIG. 7 shows in detail the construction of one form of foam dispensingunit for use in the machinery of FIGS. 2 and 3 generally identified byreference numeral 8 in said Figures.

FIG. 8 is an isometric sketch of one form of machine adapted to thecontinuous production of the workpiece in situ by the spiral winding ofa ply, with parts of the machinery cut away to show their internalconstruction, and

FIG. 9 is an enlarged isometric view of a mandrel suitable for use inthe machine of FIG. 8.

Referring to FIGS. 2 and 3, numeral 1 is a roll of ribbon on which theribbon is stored and from which it is delivered, 2 is the ribbon beingfed in the direction of the arrow from the roll on to a table 3 on aframe 4 which is pivoted at the mid point of one end directly under thelongitudinal axis of the advancing workpiece at 5 and the other end ofwhich is free to rotate round the pivot point on wheels 6 at least oneof which is driven by a handwheel 7 via a worm and pinion (not shown),shaft 70 and chain and sprockets generally identified as 7b. Attached tothe table is a canopy 17 through which the ribbon passes and mounted onthe canopy and indicated generally by reference numeral 8 is the foamdispensing means described in more detail below with the aid of FIG. 7.The nozzle of the foam dispensing means projects into the canopy asshown and vents 17a, which are attached to extractor pumps (not shown),are provided for removing any vapours and overspray from the foamableplastic composition. The vents are arranged to prevent build up ofoverspray on the sliding surfaces of the foam-dispenser to avoidclogging the moving parts. 9 is the foam-forming composition depositedon the surface of the ribbon leaving part 10 of the width uncoated foruse as the overlap for adjacent ribbon windings. The coated ribbon maybe heated by heaters (not shown) which may be above or below the tablebetween the foam dispensing means and the workpiece, and is drivenforward by a vacuum feed device, generally indicated by referencenumeral 11, which is attached to the table and is described in moredetail below with the aid of FIG. 6.

The coated ribbon then passes around an advancing tubular or rod-likeworkpiece, e.g. a plastic tube, 12, to a form a composite product 12awhich in the case illustrated is of regular annular cross-section. Theangle between the table 3 (and hence the ribbon 2) and the long axis ofthe workpiece 12 is such that successive windings of the foam coatedwidth of ribbon do not overlap but are closely adjacent and preferablyabut each other; the gap, if any, between them being not greater thanthe width of the nncoated width of ribbon which overlaps the precedingwinding.

The workpiece is supported by and fed to the winding station with acombination of linear and rotary motions by a first drive assemblyindicated generally at 13. Subsequent to the application of the foamcoated ribbon, the thus coated workpiece is supported and withdrawn fromthe winding station by a second drive assembly 14 the rotary and linearprogression components of which are preferably coupled to thecorresponding components of the first drive assembly. The detailedconstruction of one of the rotary drive assemblies is shown in FIGS. 3,4 and 8, and described further below.

Optionally, the product may be heat treated e.g. by use of an over (notshown), and may be sawn into lengths by saw 15 pivotable on shaft 16 andadapted by means not shown to travel with the product while sawingthrough it.

For example, the saw may be mounted on rails so that it may travelalongside the composite product and may be linked to an abutment whichis engaged by the front end of the product and moved by it. Actuation ofthe saw may be by microswitch triggered by the passage of the compositeproduct or may be on a time switch basis. On completion of the sawing,the saw will be retracted speedily to its rest position ready for thenext cut.

The product is supported by a plug which fits into its end, the plugbeing mounted on a trolley 18 running on rails 19.

THE DRIVE ASSEMBLIES A suitable drive assembly for the workpiece and thecomposite product is now described in more detail and with reference toFIGS. 3, 4 and 8. Each drive assembly generally represented by referencenumerals 13 and 14 in FIG. 2 comprises a base consisting of a base plate20 carrying two saddle end plates 21, the upper surface of each of whichis concave arcuate to receive a cylindrical body rotatable about itsaxis which is horizontal. At a pluraelity of points round the radius ofthe are are mounted horizontal eccentric pins 22 carrying load-bearingball races 23. Accurate positioning of the ball races to receive thecylindrical body may be achieved by adjustment of the positions of theeccentric pins.

At the bottom centre of the arcuate top surface of each saddle plate,there is an embrasure in which is mounted a thrust bearing 24 on avertical axis.

Rotatably mounted on the saddle plates and supported by the load bearingball races 23 is the first rotatable unit, or cage, which comprises anannular frame 26 linked by radially disposed parallel pairs of tie rods27 to the inwardly projecting annular flange or end plate 28 of acylindrical housing 29. The annular frame and the housing each rest onthe load-bearing ball races 23 mounted in the saddle end plates of thebase and the unit is located laterally by outwardly projectingcircumferential rails 30 on the annular frame and the housing whichco-operate with the thrust bearings 24 on the saddle end plates. Theentire cage is rotated by means of a sprocket 31 attached to the annularend part 26 and driven through a chain and second sprocket by a motornot shown.

The propelling means comprise a series of impellers each of which isslidably mounted on a pair of the tie rods 27. In each case the assemblycomprises a pair of slippers 32, and pivotably mounted on each slipper apair of parallel drop arms 33. The pairs of drop arms support betweenthem at their free ends a frame 34 which lies parallel to the cage axisand has at each end an axile on which is mounted a roller 35, 35(a). Therollers support an endless gear belt 36 which runs parallel to the cageaxis and is backed by a platen 36a along its inner run (that is, thatpart of its run which is nearer the axis of the cage). Roller 35 isdrivably connected by means of a sprocket 37 (see FIG. 8) and chain 38to a second sprocket driven by bevel gear 39 mounted on the inner wallof the cylindrical housing 29. The frame 34 is pivotahle about an axispassing through the centre of the second sprocket by means of a radiusarm.

The endless belt comprises a substantially inelastic incompressiblebacking belt 36b on the outer surface of which is a series ofresiliently compressible foam rubber pads 360. This arrangement providesthe tolerance to accept some change in the cross-sectional size of theworkpiece or product without requiring any alteration to the positioningof the impeller relative to the axis of the unit. In particular itallows flanged, spigotted and ribbed workpieces such as flanged pipes tobe handled. The inwardly facing surface of the belt is ribbed forco-operation with outwardly projecting ribs on the driving roller forpositive drive. The distance of the endless belt from the axis ofrotation of the cage is determined by the location of the slippers 32 onthe tie rods 27. The slippers may be adjustably and lockably located,for example, by means of the threaded rod 40 (see FIG. 8).

The cage preferably carries at least three, and preferably fourimpellers (as shown, for example in FIG. 3), in radially disposedpositions. If desired, the position of all the impellers relative to theaxis of the unit may be adjusted simultaneously by means of an endlesschain 41 co-operating with sprockets 42 fixed on the end of eachthreaded rod 40, and driven by a motor or a handwheel. Alternatively,the positions of the impellers may be adjusted separately whereby rods,pipes and tubes of noncircular, polygonal or even asymetriccross-sectional shape may be accommodated.

Rotatably mounted in the cylindrical housing 29 of the cage is thesecond unit. This comprises an annular wheel 43 (that is a gear ringwith the teeth facing inward) located by means of ball races 44, 45,mounted on pins located round the circumference of the wheel, bearingrespectively on inwardly facing circumferential rail 46 on the insidewall of the housing and the flanged end 47 of the housing. The annularwheel is attached to a sprocket 48 drivably connected to a motor by achain and sprocket and meshes with epicyclic or planet gears 49 each ofwhich is drivably connected to the bevel gear 39 which in turn isdrivably connected by chain and sprockets to the driving roller for oneof the endless belts as previously described.

Referring to FIG. 5, the power for driving the assembly may be providedby a motor (D) through two variable speed gearboxes (E) and (G). Thepower olftake for the cage (or first unit) is taken from the drivenshaft of the first variable speed gearbox (E), via a further reductiongear (F) while that for the second unit (annular wheel) is taken fromthe driven shaft from the second variable speed gearbox (G), if desiredvia another reduction gear (H).

As described in more detail below the drive to the rib bon feed devicemay also be taken from the same motor in which case it is desirable toprovide a clutch between the drive to that device and the drives to thedrive assemblies so that sequential start up of these is possible.

In the machinery as shown in FIG. 2, the drive assemblies are mountedone anterior to and the other beyond the ribbon winding station.Preferably they are coupled together so that the drive to the cages inthe two assemblies are coupled to operate at the same rotational speedand the drives to the annular wheels in the two assemblies are coupledto operate at the same rotational speed. Thus, referring to FIG. 5,drive shaft (1) is connected to the cage (or first unit) of each driveassembly and the drive shaft (2) is connected to the annular wheel (orsecond unit) of each assembly.

Alternatives to the drive assembly means exemplified in the embodimentdescribed above and illustrated in FIGS. 3, 4 and 8 will be apparent tothose skilled in the art. For example, the sprocket and chain drives tothe cage and annular wheel may be replaced by circular racks andappropriate gear trains; the endless belts may be replaced by linearlyarranged sets of rollers; the bevel gear between the annular wheel andeach endless belt may be replaced by worm and pinion gears; the annularwheel may be replaced by a circula rack; the means for adjusting thedistance of each endless belt from the rotational axis of the cage maybe hydraulic; the resilient pads on the endless belts may be profiled tothe outside shape of the workpiece. In yet a further alternative, meansmay be provided for adjusting the disposition of the impellers (endlessbelts) round the circumference of the cage. For example, 24 alternativepositions may be provided at intervals round the cage, up to (say) any 8of which may be occupied. Thus, for instance, for handling a workpieceof circular cross-section or for handling hexagonal or dodecagonalworkpiece, 6 positions may be occupied at 60 intervals; for handlingsquare, rectangular, octagonal or dodecagonal workpieces, 4 or 8positions may be occupied at 90 or 45 intervals. In another, andpreferred alternative, the distance of each impeller from the rotationalaxis of the cage may be adjusted without changing its longitudinalposition, e.g. by suspending each impeller from a pair of tie rods by apantographic linkage.

In operation, the position of each radially disposed impeller on thefirst drive assembly is adjusted to accommodate the workpiece, e.g. rod,pipe, tube or channel, and the position of each radially disposedimpeller on the second drive assembly is adjusted to accommodate thecomposite product, which will be larger in crosssection than theoriginal workpiece. The gearboxes E and G are then set to provide therequired rotational and longitudinal speeds and the motor is switchedon.

It will be understood that if the cage in each device is kept stationaryand only the annular Wheel is rotated, no rotational movement will betransmitted to the workpiece or product which will simply be movedforward along its axis. Similarly, if the cage and annular wheel arerotated at the same speeds, the workpiece or product will be rotatedwithout any l n Progression Thus by suitably operating the variablespeed gearboxes, e.g. Kopp variators, the workpiece or product may bemoved with any desired combination of linear and rotational rates up tothe maximum rates of linear motion and rotation possible on the machine.

By the use of coupled drive assemblies, the workpiece may besubstantially isolated from the influence of outside forces while it isbeing treated at the ribbon winding station. Furthermore, provided thedistance of each radially mounted impeller from the axis of the cage ineach assembly is adjustable the assemblies can readily accept workpiecesof widely varying size and crosssectlonal shape. In particular,workpieces of irregular crosssectional shape may be accommodated as maycomposite products which differ from the workpiece not only incross-sectional size but also in cross-sectional shape. Providcd thereare at least three radially disposed impellers in each unit, and thedistance of each set of impellers from the axis of the cage issynchronously adjustable, the machlnery also has automatic centeringcap-abilities. Another advantage is that the drive assemblies may becoupled and uncoupled with ease and may be arranged to operate either atconstant pitch or at constant linear or angular velocity and variablepitch. In the much preferred case where the impellers have resilientdriving surfaces, eg as m the case of endless belts with foam rubberpads, workpieces of variable girth may be accommodated without themachinery jarning or getting out of phase. In particular, the assembliesmay then accommodate flanged and spigotted pipes and tubes, and pipesand tubes having radial ribs or other protuberances. Furthermore, thepro- VlSlOI] of this resilience allows for very delicate handlingthereby allowing the assemblies to be used with workpieces and compositeproducts of fragile construction. At the same time, the machinery isalso robust thereby allowlng the handling of heavy workpieces andcomposite products and hence providing very great versatility.

These and other advantages make the drive assemblies described aboveparticularly suitable for use in the treatment of workpieces inaccordance with our invention. In the formation of spiral windings byfeeding a ribbon on to a rotating advancing rod-like or tubularworkpiece, for example, any inadvertent change in speed of advance orspeed of rotation of the workpiece may upset the winding, possiblyrendering the article valueless and even damaging the ribbon and/orjamming the machinery. The occurrence of such inadvertent changes issubstantially reduced by the use of the assemblies in coupled operatlon.Furthermore, by use of these drive assemblies the application of anyundue compressive, shear or torsional force to the foam at the nipbetween the rib-bon and the workpiece is substantially reduced therebyreducing the danger of deforming or collapsing the cell structure andcausing a drop in physical properties, espezially bond strength andcompressive strength of the THE VACUUM RIBBON FEED DEVICE A suitablevacuum feed device for the foam-coated ribbon 1s now described in moredetail and with reference to FIG. 6 of the accompanying drawings. Inessence it comprises a porous endless belt (which is shown with partcut-away to expose the interior of the device) and means for applyingvacuum to the underside of the belt on that part of its run in which itis intended to drive the ribbon forward, whereby the ribbon is held tothe belt by suction.

In accordance with one embodiment, it comprises a frame 50 supporting anopen-topped vacuum box 51. The top of the box is preferably trapezoid inplan as shown by the discontinuous lines, two opposing sides beingsubstantially parallel to the long axis of the ribbon, a third sidebeing substantially perpendicular thereto, and the fourth side beingsubstantially parallel to the long axis of the workpiece to allow formaximum benefit to the obtained from the device as a means for guidingas well as feeding the ribbon. In an alternative and preferredembodiment (not illustrated), that end of the box intended to bepositioned nearest the workpiece is covered by a plate one edge of whichis arranged to define the top edge of the box at that end and to remainparallel to the long axis of the workpiece irrespective of the angle ofthe long axis of the ribbon thereto.

The vacuum box is provided with ports 52, 53 connected by tubes to avacuum pump, not shown. At each end of the box along the line of thelong axis of the flexible ribbon is mounted an axle 54 transverse to thelong axis of the ribbon. Each axle bears a pair of toothed rollers 55,56 (one of each pair being shown) and the rollers are rotatably mountedthereon by means of ball races. Each pair of toothed rollers supports acorrespondingly toothed drive belt 57 (one is shown) and these in turnsupport an endless belt 58 of which at least that part of the Widthwhich covers the vacuum box is of porous or perforated material. Alongits top run, the belt is arranged to rest snugly on the open top of thevacuum box. The edges of the open top of the vacuum box may be providedwith vacuum seals to reduce vacuum leakage between the mand theundersurface of the endless belt. Means may also be provided forsupporting the endless belt during its travel over the open top of thevacuum box, for example by fitting the top of the box with a perforatedor slotted lid or by providing a plurality of parallel longitudinal ribsin the box, as shown.

At least one of each pair of toothed rollers is driven by means notshown from a motor through a variable speed gearbox, e.g. a Koppvariator. Preferably, the drive is taken from the drive to the cage ofthe drive assembly for the workpiece and/or composite product through avariable speed gearbox (K), as indicated in FIG. 6, such that for anygiven ribbon width and outside diameter of the composite product (whichtogether determine the setting for the variable speed gearbox K), therate of forward movement of the ribbon may be synchronous with the rateof revolution of the workpiece (or composite product).

Preferably, the frame of the vacuum feed device is pivotable in thehorizontal plane about the axis of the workpiece where the ribbon is fedon to it. Ideally, the pivot axis is the vertical axis which passesthrough the longitudinal axis of the workpiece and the centre line ofthe ribbon at the point where the ribbon is fed on to the workpiece. Ifthe device is thus pivoted, both rate and angle of feed of the ribbonmay be controlled by it, and that edge of the vacuum box intended to beparallel to the longitudinal axis of the workpiece, or substantially so,is positioned as near as possible to the vertical plane passing throughthat axis. Conveniently, the feed device is located on the table 4, asshown, which is pivoted about the desired axis.

For use with the ribbon drive device the machinery may also containmeans responsive to incoming information consisting of the desiredoutside diameter (D) of the composite product and the effective width(w) of the ribbon (that is, the width of the ribbon less than used foroverlap, if any) to set the required angle of feed of the ribbon (9)automatically in accordance with the relationship While the top of thevacuum box is preferably trapezoidal in plan for the reasons givenabove, other crosssectional shapes may also be used.

In operation, the angle of the vacuum feed device to the longitudinalaxis of the workpiece is set in accordance with the relationshipreferred to above (e.g. by suitably adjusting the position of the tableto which the device is attached), the ribbon is positioned on top of theendless perforated belt, vacuum is applied to hold the ribbon to thebelt and the belt is put into motion at the appropriate speed havingregard to the outside diameter of the product, the width of the ribbonand the rate of revolution of the workpiece, thereby driving the ribbonforward at the desired rate and angle.

THE FOAM DISPENSING UNIT One suitable form of foam dispensing unit, eg,for use with a foamable mixture based on a curable plastic composition,e.g. polyurethane or polyisocyanurate, is now described in more detailand with the aid of FIG. 7. It comprises a frame 59 having mountedthereon a pair of parallel rails 60 arranged parallel with the directionof movement of the ribbon. Slidably mounted on, and lockable at anydesired position along, these rails are two slippers 61 linked by asecond pair of rails 62 at right angles to the first pair, this lastpair having slidably mounted thereon a sliding head 63, the arrangementof rails and slippers thus being such that the sliding head 63 ismovable forwards and backwards across the width of the ribbon and theslippers 61 are movable in the direction of travel of the ribbon. Thesliding head carries the foam dispensing nozzle 64 which is connected toa mixing head 65 adapted to receive and mix the separate components ofthe foamable composition. The sliding head is fixed to a piston 66slidiably mounted in cylinder 67 attached to slipper 61, and inoperation reciprocated by air pressure or other suitable means. Thetravel of the sliding head is controlled by microswitches 68 carried bysliding blocks 69 whose positions are adjustable and lockable by meansof screwed rods 70 threaded through slippers 61. The microswitchesoperate the air valves or the other means for reversing the travel ofthe piston 66 in cylinder 67.

A modified version of the machine of the invention, in which the tubularworkpiece is generated in situ by helical winding of one or more plies,e.g. of paper or plastic, is now described in more detail with referenceto one embodiment thereof and with the aid of FIG. 8.

Referring to FIG. 8 reference numerals 1 to 48, where given, have thesame significance as in FIGS. 2, 3 and 4. 71 is a roll from which aflexible ply 72, e.g. of paper, may be withdrawn by a vacuum feed device73 of the type described above and illustrated in FIG. 7. This device ismounted above the ribbon such that the vacuum is applied to the topsurface thereof. It is supported by a frame pivotable about a verticalaxis 74 which ideally passes through the centre line of the ribbon andthe longitudinal axis of a mandrel 75 on to which the ribbon is fed atan angle of less than to the axis thereof and about which it is wound toform helical windings 76. 77 is a roll of adhesive tape from which tapeis fed on to the paper windings on the mandrel at the joints of thegenerated helices in order to bond them together to form a unitarytubular structure.

To aid the movement of the ply around and along the mandrel, it may bedesirable for the mandrel to be tapered towards its tail and/or toprovide a layer or cushion of fluid, e.g. air, between the mandrel andthe ply. For example, compressed air may be supplied to the interior ofthe mandrel by a conduit and thence out through its surface by means ofseveral passages through the wall. Alternatively, the mandrel may behollow and porous (e.g. of sintered or perforated metal) and providedwith a supply of compressed air to its interior.

Where the ply is of flimsy material such that the workpiece formed fromit is not capable or scarcely capable of supporting itself, it will bedesirable to support it while feeding on the coated ribbon and until thefoam is sulficiently set for the composite product to beself-supporting. This may be achieved by arranging for the mandrel 77 toextend as far as or even beyond the ribbon winding station e.g. into therotary drive unit 14. It is then especially desirable for the mandrel tobe tapered and/or to provide a fluid layer or cushion between the plywindings and the mandrel surface because the application of the coatedribbon may tend to press the ply windings against the surface thusrestricting their ease of motion along the mandrel.

One suitable form of mandrel will now be described in more detail withthe aid of FIG. 9. The mandrel comprises a cantilevered shaft 80 rotablymounted by means of ball races 81 on a frame 82. Slidably mounted onsaid shaft are a number of hollow cylindrical units, 78, 79. Thecylindical wall of each of those forming the tail (or unsupported) endof the mandrel is porous, e.g. of perforated metal while those of thehead units 78 are impermeable and of slightly larger diameter e.g. 0.01to 0.04 inch larger, than those forming the tail. There is thus formed astep between the head and the tail which defines an annular gap for acushion of air provided from a compressed air supply and suppliedthrough the porous walls of the tail units by means of a conduit 83inside and running the length of the shaft 80, and ports 85 at pointsalong the length of the conduit connecting with the hollow interior ofthe tail units. The conduit is provided with a valve 84 for controllingthe compressed air supply and, in a preferred embodiment, the orifice ofeach port 85 is adjustable so as to be able to provide differential airpressure along the length of the tail.

The shaft may be rotated by power means, e.g. a variable speed motor, inwhich case at least the head units are arranged to rotate with theshaft. In the embodiment illustrated both head and tail units arearranged to rotate with the shaft by means of tie rods 86 running thelength of the shaft and fixed to the flange 87. Alternatively, the unitsmay be mounted to rotate with the shaft by friction, e.g. by clampingthe units together by screwing on an end plate 88 which presses theunits together and against the flange 87.

It will readily be appreciated that by providing a series of sets ofcylindrical head and tail units of appropriate dimensions, the lengthand diameter of the mandrel may be arranged to accommodate plies ofvarious materials to form workpieces of various diameters. In a veryconvenient embodiment, the head part of the mandrel may comprise tailunits with impermeable sleeves of the appropriate thickness fitted overthem.

Cantilevered mandrels of the kind herein described are the subject ofour copending British patent application No. 9,956/69.

In operation, the ply forming the workpiece is fed on to and round thehead of the mandrel and adjacent ply windings are bonded together byadhesive tape. The foam coated ribbon is then fed on to the spirallywound workpiece being formed, preferably at a position such that atleast part, but not all, of the width of the foam coated ribbon extendsover the tail of the mandrel. With paper ply and foam coated paper orplastic ribbon, we have found air pressures between about 20 and 60lbs./sq. in. suitable for the air cushion. Higher pressures tend torender the spiral winding of the ply dilficult to control. The mandrelis rotated at a speed at least equal to the speed of rotation of thedrive assembly for the product.

Where the ply is of relatively stiff material and the tubular workpiecewound from it substantially self-supporting, the mandrel 75 may bedispensed with. If desired, the ply may then be fed directly into thefirst rotary drive assembly 13 at such an angle that the tubularstructure is generated within the unit. For use in this embodiment, itis preferred that the radially disposed impellers of this rotary driveassembly (the endless belts, for example) are so disposed and profiledas to proscribe a substantially uninterrupted circle.

In accordance with one method of putting into operation the process ofour invention, the angle at which the coated ribbon is to be fed to theworkpiece is determined and set, and the desired rates of linear androtary motion of the workpiece and composite product and linear motionof the ribbon are calculated and set on the KOPP variators orcorresponding speed-controlling devices. The workpiece to be sheathed isplaced in position across the ribbon winding station and the ribon isdrawn by hand off its supply roll and under the foam dispenser. The foamdispenser is then started and the motor driving the vacuum feed devicefor the ribbon is started up, but leaving the clutch disengaged so thatthe drive assemblies are disconnected from the motor. The foam coatedribbon is guided along the table and on to the vacuum feed device and isthen withdrawn from the vacuum feed device, fed under and round theworkpiece and the free end fixed thereto at a suitable angle by anysuitable means, e.g. adhesive tape. The two drive assemblies from theworkpiece and composite product are then put into motion by engaging theclutch. In an alternative method, particularly suitable where theworkpiece is being generated in situ by extrusion or by spiral windingof one or more plies, the rotary drive assembly and mandrel (where used)may be set in motion first and the ribbon passed round applied to theworkpiece while it is in motion.

As will be appreciated, many alternatives to and modifications of theprocesses and machinery specifically exemplified with reference to FIGS.2 to 9 may be used without departing from the nature of the invention.Some are now mentioned.

More than one ribbon may be fed on to the workpiece and one or more ofthe ribbons may be coated with a foamable composition.

Each coated ribbon may have one or more than one coating of foamcomposition applied.

Reinforcement may be introduced by inclusion of fibers, wires, tapes orthreads of metal, carbon, graphite, glass or plastic and thereinforcement may be applied longitudinally or helically and in one ormore layers.

The workpiece may be treated, e.g. with a protective coating or anadhesive or a wetting agent, before the ribbon is applied.

The ribbon need not be fiat but may have a complex cross-section, e.g.with ribs running along and/or across the ribbon, or with dimples.

The machinery may be adapted so that the workpiece moves upwards ordownwards in or near the vertical plane rather than in the horizontalplane.

Filler materials other than foams may be used, and may be fibrous,granular, particulate or fluid (the last preferably with the workpiecemoving in the vertical plane).

Depending on the nature of the workpiece, the tiller material and theribbon, and the presence or absence of other reinforcing or decorativeadditions, a wide variety of products having a wide range of propertiesand uses is obtainable from our process. Examples of uses are lagging,air ducting, hot water pipe, cold water pipe, sewage pipe and packaging.

What we claim is:

1. Machinery for the production of composite products comprising incombination (i) support means for the machine components, (ii) means forsupporting a rod-like or tubular workpiece, (iii) means for continuouslymoving said workpiece along its longitudinal axis past a ribbon windingsation, (iv) means for simultaneously rotating said workpiece about itslongitudinal axis, (v) continuous supply means for a flexible ribbon,(vi) drive means for feeding the ribbon forward to the rotatingadvancing workpiece at the ribbon winding station at a preselected rate,(vii) means for guiding the ribbon tangentially onto the workpiece at apreselected angle of less than to the longitudinal axis thereof at theribbon winding station, (viii) means for providing a filler material,especially foam, in the space between the workpiece and the sheathformed therearound by the spirally wound ribbon, and (ix) guide andsupport means for the composite product so formed, the drive means (vi)comprising a frame carrying (it) 19 a vacuum box open at the top, (xi)beyond opposite ends of the box parallel rollers for supporting anendless belt, (xii) means for driving at least one of the rollers,(xiii) an endless belt of porous or perforated material adapted totravel across the open top of the vacuum box, (xiv) preferably a vacuumseal between the top edges of the box and the belt, and (xv) means forconnecting the interior of the box to a vacuum pump.

2. Machinery as claimed in claim 1, wherein the ribbon is supportedduring the deposition of the foam composition and located laterally on atable which is pivotable in a horizontal plane about a vertical axiswhich passes through the longitudinal axis of the workpiece and thecenter line of the ribbon where it is fed on to the workpiece, the saidtable being slightly convexly curved along its length.

3. Machinery as claimed in claim 2, wherein the drive means for feedingthe ribbon to the workpiece is located upon the table whereby the ribbonis supported.

4. Machinery as claimed in claim 1, wherein the means for continuouslymoving the workpiece past the ribbon winding station and for rotatingthe workpiece is a drive assembly comprising (a) a base having mountedthereon (b) a first unit and a second unit through each of which theworkpiece may move along its longitudinal axis, each of said units beingseparately rotatable about said axis, and (c) means for rotating each ofsaid units around said axis, and wherein the first unit has mountedthereon means for propelling the workpiece along its longitudinal axis,and the second unit is co-operatively engaged to the propelling meanswhereby in operation the propelling means is set in motion by causingrelative rotary motion between the first unit and the second unit andthe speed of the propelling means is proportional to the difference inthe rotational speeds of the first and second units.

5. Machinery as claimed in claim 4, wherein the units of the driveassembly are capable of being synchronously coupled so that at anylinear throughput velocity or rotational speed the pitch of the helicalpath along which the surface of the workpiece or product is movedremains constant.

6. Machinery as claimed in claim 4, wherein the means for propelling theworkpiece along its longitudinal axis comprise a plurality of impellersgenerally parallel to and radially disposed relative to the axis ofrotation of the first unit.

7. Machinery as claimed in claim 6, wherein there are at least threeimpellers in the form of endless belts.

8. Machinery as claimed in claim 6, wherein means are provided foradjusting the distance of each impeller from the rotational axis of thefirst unit.

9. Machinery as claimed in claim 8, wherein means are provided foradjusting the distance of each impeller from the rotational axissimultaneously with the distance of each other impeller therefrom.

10. Machinery as claimed in claim 4, wherein the second unit of thedrive assembly comprises an annular wheel which is co-operativelyengaged to at least one of the radially disposed impellers.

11. Machinery as claimed in claim 4 wherein a second such drive assemblyis provided at a position beyond the ribbon driving station to drive thecomposite product.

12. Machinery as claimed in claim 11, wherein the two drive assembliesare coupled so that the means for advancing the workpiece to the ribbonWinding station and the means for withdrawing the composite product fromthe ribbon winding station operate at the same linear velocity, and themeans for rotating the workpiece and composite product operate at thesame rotational speed.

References Cited UNITED STATES PATENTS 3,385,179 5/1968 Roe 156-195 X3,480,493 11/1969 Bauer et al. 156-429 X 3,687,765 8/ 1972 MacLean etal. 156-392 X 3,687,778 8/1972 Cichoski et al. 156-4 29 X EDWARD G.WHITBY, Primary Examiner US. Cl. X.R.

